2 THE VOYAGE OF H.M.S. CHALLENGER. 



I am bound to add that my investigations have not been pursued as far as 1 had 

 desired. 



1. This is, in the first place, due to the unsatisfactory state of some of the specimens, 

 either in consequence of prolonged preservation, or because the soft parts had been 

 .somewhat injured in the removal of the .shell. 



2. Furthermore, certain forms were represented only by single specimens, the 

 rarity of which made it necessary to retain them as intact as possible. 



Finally, the short space of time allowed for the accomplishment of my work forced 

 me to hurry on with the direct examination, and to defer certain accessory researches 

 which would have increased the interest and completeness of the results. 



